Electrical measuring instrument



A. G. QQNRAD ELECTRICAL MEAsuRmG-INSTRUMENT j Filed Aug. 4, 1944 Patented Aug. v14, 1945 carico STATES PATENT ortica 2,382,295 ELECTRICAL MEASUPING INSTRUMENT Albert G. Conrad, Mount Carmel, Conn., assigner to Manning, Maxwell & Moore, Inc., Bridgeport, Conn., a corporation o! New Jersey Application August 4, 194i, Serial No. 548,035

(Cl. T11-95) 11 Claims.

The present invention relates to improvements in electrical measuring-instruments such, for inv stance, as ratio-meters, power-factor meters,

and other electrical'` measuring-instruments in which it may be desired to automatically reset an indicator without normally imposing a load thereon. a

One of the objects of the present inventionv is to provide a superior electrical measuringinstrument having simple, reliable and effective means for automatically resetting the indicator thereof without interfering with the accurate functioning of the instrument.

Another object of the present invention is to provide an electrical measuring-instrument with superior means of the character referred to, and which willfunction despite wide variations in the applied voltages.

A further object of the present invention is to provide a superior electrical measuring-instrument of the character referred to which'will not appreciably uctuate or hunt when sudden changes occur in the applied voltages.

Stili another and more specific Vobject of the present invention is to provide a superior ratiometer lhaving automatic means for resetting the indicator thereof, and so constructed and arranged as not to interfere with the accurate functioning of the ratio-meter.

A still further specific object of the present invention is to provide a superior ratio-meter havand are respectively locatedvon opposite sides of 4a shaft or arbor I2. The coil-sections IIa and IIb of the coil Il also extend in parallelism with each other on respective opposite sides of the shaft I2, but are obliquely disposed with respect to the coil-sections Illa and Ib.

In the instance shown, the coils II) and l I and hence their respective coil-sections `IIl'a---Ib and IIa-I Ib are of rectangular ring-like form and are so arranged that the coil-sections IIa-and IIb extend obliquely through the coil-sections Illa and Ib. Thus, the shaft or arbor I2 extends vertically in parallelism with the faces of the coil-sections iDa-Ib and IIaf--Iib and is enclosed, so to speak, within the substantiallyrectangular outline provided by the respective central portions of the four coil-sections above referred to. y

The upper end of the shaft I2 is provided with a radially-extending rigid pointer or indicator I3 adapted to sweep over an 'arcuate series of indicia I4, which latter are printed or otherwise applied to the surface of a dial-plate I5.v

` Adjacent each 4ot the ends of the series of indicia I4 the dial-plate I5 is provided with two upstanding stop-pins I8 and I1; which are adapted to be engaged by and to limit the moveing resetting-means of the character referred to, combined with means for minimizing the uctuating or hunting eilects of rapid changes in the applied voltages.

With the above and other objects in view, as will appear to those skilled in the art from the present disclosure, this invention includes al1 features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanying drawing. in which certain modes of carrying out the present invention are shown for illustrative purposes: l

Fig. 1 is a schematic view of an electrical measuring-instrument in the form of a ratio-meter embodying the present invention.

'Ihe particular electrical measuring-instrument chosen for purposes of making clear one vform of the present invention as illustrated in the accompanying drawing, includes two complemental coils I0 and II respectively divided into coil-sections IIla--Ib and IIa-I1b. 'I'he coil-sections Illa and IIib extend parallel with each other in laterally-spaced-apart relationship ment of the pointer I3. l

The coil-sections Illa and IDb of the coil IB are electrically interconnected as at I8, while the coil-sections IIa and IIb of the coilA Il are similarly interconnected at I9. One terminal of the coil I0 isconnected to a line-wire 20 which is the complement of a second line-wire 2|, both of which lead to any suitable' source Vof A. C. or D. C.'voltage which it is desired to have applied to the electricalv measuring-instrument shown.

The remaining terminal of the coil III is interconnected by a wire 22 to one of the terminals of the coil II, and the said wire 22 is connected by means of a wire 22 to the adjustable contact 2l of a resistor 25. The remaining terminalof the coil II is, as shown, connected to the linewire 2|. The resistor 25 has its respective opposite terminals connected by wires 26 and 2l to the complemental line-wires 20 and 2|.

Theparts I0 to I9 inclusive, above described,

compose what is commonly referred to as a ratio-meter. In the instance shown, therefore, the forces respectively developed by the coils I0 and II at any given instant, 'while variable relative to each other, are, however. always such as t0 oppose each other in their respective eiorts to move an .armature 28 rigid with and extending diametrically with respect to the shaft l2.

As schematically illustrated in the accompany- 'ing transversely between the pole salients 9| and 32 and hence diametrically across the dampingcup 29, is a bridge-member B preferably formed of non-magnetic material and rigidly secured at its respectiveopposite ends to the pole salients Si and 32 just referred to. Located within the damping-cup- 29 and supported by the bridgemember 83 is a second or bar-like damping-magnet M having its respective opposite ends aligned with the pole saliente SI and 82 vci? the dampingmagnet 39. l

Preferably, both the damping-magnet 8@ and the damping-magnet 94 are formed of a permanent magnet material, though one thereof may be formed of non-permanent magnet material such. for instance, as soft iron.

The inner face of the pole salient 9|' and the adjacent face of the damping-magnet 34 are spaced from each other to freely-accommodate between them the ange of the damping-cup 29.

Similarly, the inner-'face of the pole salient 92o! the adjacent face of the damping-magnet 3c is spaced from the adjacent face of the bar-like damping-magnet 14 to also accommodate the iiange ofthe damping-cup 29.

From the foregoing it will be seen that the turning of the cup in the gaps. between the damping-.magnets 39 and 3A will develop in the flange of the said cup. eddy-currents which oppose the rapid movement of the-damping-cup and hence also oppose the rapid movement of the shaft l2 and pointer I3. The more rapid the movement, the greater the opposing force acting as a damperor brake. In this manner, undue fluctuations in the movement of the pointer Il are eliminated without interfering with the-cor,- rectas functioning of the latter and its associated pa assassin a wire to the line-wire 29, and having its o pposite terminal connectedby means of a wire Mn to the line-wire 2|. In instances where the measuring-instrument islto be used in connection with alteratingcurrentl it is preferred that the retracting-armature 98 and the retractingmagnet 39 be formed of sintered iron, or of lam- ,inated iron of soft steel, in order to avoid undue heating under the influence of such alternating current.

Intermediate the restoring-arm 3 and the retracting-armature 3B, the shaft 31 is provided with a hub Il rigidly connected to the said shaft and having connected to it in turn, the inner; end of a spiral restoring-spring 46 having its -outer end secured to a normally stationary pin 41. 'I'he restoring-spring 48 is of spiral form and corresponds generally in character to so-called hairsprings" common fin clocks and electrical instruments.

"A wire e8 and a wire 49 respectively extend inwardly from the line-wires 2b and 2| to the complemental contacts of a double-pole switch 59. The blades of the said switch 50 are respectively connected to the adjacent ends of similar coils 5|" and B2, while the opposite terminals of the said coils are connected together and jointly connected by means of a wire Esto the wire 23 leading to the contact 24 ofthe resistor 2E.

The coils 5| and 52 correspond 'in their respective impedances to the coils I0 and Il, and provide a duplicate or dummyl load for purposes as will more fully hereinafter appear.

Preferably. all of these elements above described would be enclosed within a suitable single case, in vwhich case the so-called line-wires 2G and 2l would be provided respectively with terminals 54 and 5l, to which may be connected suitable wires providing the voltages which are to be applied to the instrument-assembly above described. l

Under the conditions shown by fulll lines in the drawing, no voltage is applied across the terminals M and I5, and hence the restoring-spring is acting through the intermediary of the shaft 31. restoring-arm restoring-pin I5, dampingcup 2l and the shaft I2, to turn the pointer I3 into zero (or other desired position) and against the stop-pin Il, vIt will be noted that under The damping-cup 2t is provided with a downwardly-extending restoring-pin, Vwhich latter is adapted to be engaged by, the outer end of a restoring-arm 39 in a manner as' will more vfully hereinafter appear.-

'I'he said restoringarm 39 is in the instance shown, rigidly attached to the upper portion of a vertical shaft 31, located in a vertical plane forwardly (as viewed in the drawing) with respect to the plane of the shaft I2. The said shaft 31 (like the shaft II) .may be supported in any suitable bearing '(not shown),

and has rigidly attached to its lower end a barlike retracting-armature 9|. The path of movement of the retracting-armature 9| is embraced." so to speak. by a U-shaped retractingmagnet 99 having laterally' spaced-apart pcie saliente 49 and 4| which are adapted to attract the-respective adjacent ends of the reti-actingarmature 9|, all in a manner as will morefully hereinafter appear.

The central portion of the reti-acting-xrlagnet 99 has extending therearo'und an 'energizing-coil 42 having one terminal connected by means of As soon as suitable voltages 'are applied to thev terminals N and It, the retracting-magnet 39 will be energized through its energizing-coil I2 and will immediately draw the retracting-arma- Y ture4 Il into alignment with the pole salients I9 and 4|. This action will.swing'the restoringarm 36 in a counterclockwise direction over into the position in which it is indicated by broken lines and. therefore, out of position to in any vway interfere with the movement of the restoring-pint! or the damping-cup A29 and its associatedJwparts.

Thus. by the described movement of the re- 'tracting-armature ll and associated parts, the tension ofthe restoring-spring 48 will be overcome to ythus leave the ratio-meter or its equivalent free to function accurately and unhindered.

When the voltage across the Vtwo .terminals Il `and l5 is c'ut oif or reduced lbelow a predetermined minimum' value, the restoring-spring 48 will assert itself and will turn the shaft I1 in a clockwisedirectlon (as viewed in the drawing), thereby causing the restoring-arm 38 to engage with the restoring-pin 35 to thus effect the turning of the pointer I3 and its associated parts, back into the position in which they are shown by full lines in the drawing.

The energizing-c0114? of the retracting-magnet 39 is preferably so proportioned, that despite wide incidentally with the said electrical actuatingmeans of the said indicator.

2. An electrical measuring-instrument, including in combination: an indicator; electrical acfluctuations in the voltages applied across the of the coils I and II of the instrument, wouldy i normally tend to cause a very rapid movement of the pointer I3 which would cause vibration of the latter in its hunting efforts to arrive at a proper value.` Such rapid movement of the y pointer I3 and the consequent hunting movements thereof, will be effectively damped-out by the eddy currents developed in the damping-cup 29 when the same is moved with respect to the damping-magnets 30 and 33. The shaft l2 and the parts connected thereto will not be prevented from functioning, but will merely be slowed down. to thus avoid the undesirable effects before referred-to.

In instances where two ratio-meters or the like would ordinarily be connected to a source of voltage, the cutting out of one such ratio-meter would be' very apt to cause inaccuracies in the ratio-meter which remains connected. To counteract such eiect and to enable a single ratiometer or the like to give accurate indications, the dummy load comprising the coils EI and E2 is provided. Thus, when another ratio-meter or y the like is cut off from the voltage source supplying the terminals 56 and 55, the conditions may be restored by closing the switch 50, and thus, in

effect, imposing a dummy load substantially equivalent to another ratio-meter.

The invention may be carried out in other specific Ways than those herein set forth without departing from the spirit and essential character'isticslof the invention, and the present embodiments are, therefore, to be considered in all i respects as illustrative and not restrictive,4 and all changes coming within the meaning and equivalency range of the appended claims are intended to beembraced therein.

I claim: i

l. An electrical measuring-instrument, including in` combination: an indicator: electrical actuating-means for deflecting the said indicator; a restoring-spring; restoring-means operated by the said restoring-spring and constructed and arranged to yieldingly hold the said indicator in a predetermined position; a retracting-electromagnet; connecting-means electrically interconnecting the said electrical actuating-means and the said retracting-electromagnet to provide for the concurrent energization of both thereof; and a retracting-armature operatively connected to the said restoring-means and to the said restoring-spring and located in the magneticeld developed by the said retracting-electromagnet, the` said retracting-armature being constructed and arranged to automatically re-tract the .said restoring-means into a retired position against the urge of the said restoring-spring when the said retracting-electromagnet is energized cotuating-means for defiecting the said indicator; a restoring-spring; restoring-means operated vby the said restoring-spring and constructed and arrangedto shift the said indicator in one direction only into a predetermined position; a re -tracting electromagnet; connecting-means electrically interconnecting the said electrical actuating-means and the said retracting-electromagnet to provide for the concurrent energization of both thereof; and a retracting-armature operatively connected to the said restoring-means and to the said restoring-spring and located in the magnetic field developed by the said retracting-electromagnet, the said retracting-armature being constructed and arranged to automatically retract the said restoring-means intoa retired position against the urge of the said restoringspring when the said retracting-electromagnet is energized coincidentally with the said electrical actuating-means of the said indicator.

3. An electrical measuring-instrument, including in combination: an indicator-shaft; an indicator carried by the said indicator-shaft; electrical actuating-means for deecting the said indicator; a first restoring-abutment carried by the said indicator-shaft; a second restoringabutment engageable with the said rst restoring-abutment to shift the said indicator into a predetermined position; a restoring-spring operatively connected to the said second restoringabutment and constructed and arranged to yield- Aingly engage the said second restoring-abutment with the saidrst restoring-abutment to shift the said indicator into a predetermined position; a retracting-electromagnet; connecting-means electrically interconnecting the said electrical actuating-means andthe said retracting-electromagnet to provide for the concurrent energization of both thereof; and a retracting-armature operatively connected to the said second restoring-abutment vand located in the magnet field developed by the` said retracting-electromagnet, the said retracting-armature being constructed and arranged to automatically retract the said second restoring-abutment into a retired position against the tension of the said restoring-spring when the said retracting-electromamg/net is energized coincidentally with the said electrical actuating-means ofthe said indicator.

4. An electrical measuring-instrument, includingincombination: an indicator-shaft; an indicator carried by the said indicator-shaft; electrical actuating-means for defiecting the said indicator; a restoring-abutment carried by the said indicator-shaft; a restoring-lever engageable with the said restoring-abutment to shift the said indicator into a predetermined position; a restoring-spring operatively connected to the said restoring-lever and constructed and arranged to yieldingly engage the said restoring-lever with the said restoring-abutment to shift the said indicator into a predetermined position; a retracting-electromagnet; connecting-means electricalarmature being constructed andarranged toV gautomatically retract the said restoring-lever into a retired position against the tension of the said restoring-spring when the said retractingelectromagnet is energized coincidentally with the said electricalactuating-means of the said indicator.

5. An electrical measuring-instrument, including in combination: an indicator-shaft; an indicator carried by the said indicator-shaft; electrical actuating-means for deflectng the said indicator; a restoring-abutment' carried by the said indicator-shaft; a restoring-lever engageable with the said restoring-abutment to shift the said Aindicator into a predetermined position; a restoring-shaft located adjacent the said indicatorshaft and carrying the said restoring-lever; a restoring-spring operatively connected to the said restoring-shaft and constructed and arranged to turn the latter to yieldingly'engage the said restoring-lever with the restoring-abutment of the said'indicator-shaft to shift the said indicator into a predetermined position; a retracting-electromagnet; connecting-means electrically interconnecting the said electrical actuating-means and the said retracting-electromagnet to provide for the concurrent energization of both thereof;

and a retracting-armature operatively connected to the said restoring-shaft and located in the magnetic field developed by the said retractingelectromagnet, the said retracting-armature being constructed and arranged to automatically turn the said restoring-shaft to retract the said restoring-lever into a retired position against the Atension of the said restoring-spring when` the said retracting electromagnet is energized coincidentally with the said electrical actuatingmeans of the said indicator.

6. An electrical measuring-instrument, includ- 4ing in combination: an indicator; electrical actuurge of the said restoring-spring when the said retracting-electromagnet is energized coincidentally with the said electrical actuating-means of the said indicator; a damping-member operatively connectedto the said indicator; and a damping-magnet associated with the said damping-member to retard the rapid movement thereof.

7. An electrical measuring-instrument, including in combination: an indicator; electrical actuating-means for deflecting the said indicator; Va restoring-spring; restoring-means operated by the said restoring-spring andconstructed and arranged toshift the said indicator in one direction only into a predetermined position; a retracting electromagnet; connecting-means electrlcally interconnecting the said electrical-actuating-means andthe said etracting-electromagnet to provide for the concurrent energization of both thereof; a retracting-armature operatively connected to the said restoring-means and to the said restoring-spring and located in the magnetic field developed |by the said retracting-electromagnet, the said retreating-armature being constructed and arranged to yautomatically retract the said restoring-meansinto a retired position against the urge of the said restoring-spring when the said retracting-electromagnet is energized coincidentally with the said electrical actuatingmeans of the said'indicator, a. damping-member operatively connected to the said indicator; and a damping-magnet associated with the said damping-member to retard the rapid movement thereof. y

8. An electrical measuring-instrumentl including in combination: an indicator-shaft; an indi- -cator carried by the said indicator-shaft; a damping-member also carried by the said indicatorshaft; electrical actuating-means for deflecting the said indicator; a iirst restoring-abutment carried by the said indicator-shaft; a second restoring-abutment engageable with the said first restoring-abutment to shift the said indicator into f a predetermined position; a restoring-spring operatively connected to the said second restoringabutment and constructed and arranged to yield/- ingly engage the said second restoring-abutment.

with the said first restoring-abutment to shift the said indicator into a predetermined position;

a ret'racting4 electromagnet; connecting-means` ment and located in the magnetic iield developed by the said retracting-electromagnet, the said retreating-armature being constructed and arrangedto automatically retract the said second restoring-abutment into a retired position against the tension of the said restoring-spring when the said retracting-electromagnet is energized coincidentally with the said electrical actuatingmeans of the said indicator; and a damping-magnet associated with the aforesaid damping-mem- Iber t retard the rapid movement thereof.

9. An electrical measuring-instrument, including'in combination: an indicator-shaft; a damping-member operatively connected to the said indicator-shaft; an indicator carried by the said indicator-shaft; electrical actuating-means for deiiecting the said indicator; a restoring-abutment carried by the. said indicator-shaft; a restoring-lever engageable with the said restoringabutment to shift the said indicator into a predetermined position; a restoring-spring operatively connected to the said restoring-lever and constructed and arranged to yieldingly engage the said restoring-lever with the said restoringabutment to shift the said indicator into a predetermined position; a retracting-electromagnet; connecting-means electrically interconnecting the said electrical actuating-means and the said retracting-electromagnet to provide for the concurrent energization of both thereof; a retractingarmature operatively connected to the said restoring-lever and located in the magnetic field developed bythe said retracting-electromagnet, the said retracting-armaturc being constructed and arranged to automatically retract the said restoring-lever into a retired position against the tension of the said restoring-spring when the said retracting-electromagnet is energized coincidentally with the said electrical actuating-means;

and a damping-magnetv associated with the said damping-member to retard the rapid movement thereof.

10. An electrical measuring-instrument, including in combination: an indicator-shaft; an

'indicator carried by the said indicator-shaft; a

the said restoring-lever with the restorlng-abutment of the said indicator-shaft to shift the said indicator into a predetermined position; a retracting-electromagnet; connecting-means electrically interconnecting the said electrical `actuating-means and the said retracting-electromagnet to provide `for the concurrent energization of both thereof; a retracting-armature operatively connected to the said restoring-shaft and located in the magnetic field developed by the said retracting-electromagnet, the said retractingrarmature being constructed and arranged to automatically turn the said restoring-shaft to retract the said restoring-lever into a retired position against the tension of the said restoringspring when the said retractins-electromagnet is energized coincidentally with the said electricalactuating means; and a damping-magnet associated with the said damping-member carried by the said indicator-shaft to retard the rapid movement oi' the latter.

A 11. An electrical measuring-instrument, including in combination: an indicator; electrical actuating-means for deilecting the said indicator; a restoring-spring; restoring-means operated by the said restoring-spring and constructed and arranged to yieldingly hold the said indicator in a predetermined position; a retractingelectromagnet; connecting-means electrically interconnecting the said electrical actuatingmeans and the said retracting-electromagnet to provide for the concurrent energization of both thereof; a retracting-armature operatively connected to the said restoring-means and to the said restoring-spring and located in the magnetic field developed by the said retractins-electromagnet, the said retracting-armature being constructed and arranged to automatically retract the said restoring-means into a retired position against the urge of the said restoring-spring when the said retractins-electromagnet is energized coincidentally with the said electrical actuatingmeans of the said indicator; a dummy-load having a resistance substantially corresponding to the resistance of theaforesaid electricalactuatingmeans; and switch-means constructed and arranged to selectively connect the said dummy-load 

